Fix licensing inconsistencies

Fix licensing inconsistencies

Some files in the source tree state that they are licensed under the
GNU LGPL.  For files included from external libraries (base64, rsvg),
this makes sense; but there are some random files in libgeda, gschem,
and gsymcheck which state they are licensed under the GNU LGPL, as well.

Since the majority of files in gEDA/gaf is licensed under the GNU GPL
and some files (e.g., libgeda/src/s_path.c) explicitly state that they
are based on LGPL'd code and an exception to the rule that gEDA/gaf,
as a whole, is licensed under the GNU GPL, I assume this is an error
and fixed the licensing information for these files.